Method and device for actuating a shift element of an automatic transmission having a start-stop means

摘要

A method for actuating a shift element of an automatic transmission having a start-stop function and a pressure medium pump driven by an internal combustion engine. The shifting elements are clutches or brakes that can be actuated by a piston which is actuated for engagement via pressure supplied to a pressure space. The pressure space is depressurized when the engine stops. To enhance start-stop operation, the shifting elements comprise an additional pressure space that acts, in opposition to the pressure space acting in the engaging direction, as a controllable restoring mechanism which can be rendered inactive, if desired. If the engine stops and the automatic start-stop function is activated, the additional pressure spaces, acting in the restoring direction, are depressurized before the pressure drop in the pressure spaces, acting in the engaging direction, of the pistons, but are otherwise permanently pressurized during driving operation.

主权项

1. A method of activating shifting elements of an automatic transmission with an automatic start-stop function, a pump (2) for supplying the transmission with pressure medium being driven by an internal combustion engine, the shifting elements (A, B), in the form of shifting clutches or shifting brakes, are in each case actuatable by an axially movable piston (10, 25), the piston being acted upon in an engaging direction by pressure within a pressure space (11, 26), and the pressure space (11, 26) acting in the engaging direction of the piston (10, 25) being depressurized when the engine stops, the method comprising the steps of:
at least in each case of the shifting elements (A, B) involved during starting processes, providing an additional pressure space (14, 29) as a restoring means which acts, in opposition to the pressure in the pressure space (11, 26) acting in the engaging direction, and which, when the engine stops and the automatic start-stop function is activated, being depressurized at a time earlier than a pressure drop in the pressure space (11, 26) that acts in the engaging direction of the piston (10, 25), but is otherwise permanently pressurized during driving operation.